/**
 * 编译看左边, 运行看右边
 */
public class App {
    public static void main(String[] args) throws Exception {
        App appCast = (App) new Child();
        appCast.print();
    }

    public void print() {
        System.out.println("Father class print method");
    }
}

class Child extends App {
    public void print() {
        System.out.println("Child class print method");
    }
}